As computers and personal computers have been significantly reduced in size from desktop models using 51/4 inch disk drives to laptop and notebook computers, the disk drives have been reduced to 31/2 inch floppy disk drives and smaller hard disk drives or DASD.
The DASD must be sealed from the ambient environment to prevent contamination from dust and other substances which might affect either the electromechanical operation of the device or contaminate the disk surface, thereby causing damage to the recordable disk surface, preventing reliable data storage and retrieval. Sealing the disk drive must be accomplished in a manner which accommodates the need to electrically connect the disk drive to the circuit which provides power to the actuator motor. Additionally, data signals must be conducted either to or from the magnetic head on the arm of the actuator, and conductors must convey the data signals between the magnetic head/disk interface and the external circuit for use by the computer or recording onto the disk.
Data signals conveyed between the magnetic head on the actuator load beam and the using circuits external to the DASD must be reliable. To insure reliability of these data signals, the DASD must have highly reliable conductive circuit paths that also accommodate movement of the actuator as the actuator positions both the slider and magnetic head relative to the surface of the magnetic disk.
As the DASD size is reduced and while continuing to provide highly reliable service, the size of all the internal and external components of the DASD similarly must be redesigned to become either more compact or eliminated. One aspect of this size reduction requires that the circuits for electrical power and data transmission must be reduced in size and thickness in order to conserve space and particularly to permit the reduction in height of the DASD. With the reductions in height and size of the DASD, electrical and structural reliability of the circuits must be maintained even as the individual DASD components are reduced, particularly the electrical circuits which include connectors and position maintaining devices. One approach to reducing the size of the electrical circuit and associated components is to eliminate some, if not all, connectors and parts or devices that have been previously required to mount the electrical circuits. As connectors are eliminated, some sources of unreliability also are eliminated. Connectors are notorious as sources of problems in electrical circuits; and by eliminating connectors from the circuits wherever possible, not only are potential reliability problems associated with those connectors likewise are eliminated but also the space provided for such connectors within the structure is no longer required.
Wherever flex cables previously have been used to conduct data and/or power to devices which move relative to a fixed portion of the flex cable, a flexible circuit has been positioned or disposed in such a manner that the flexing of the flexible cable as much as 90 degrees or more will not unduly deteriorate the electrical transmission characteristics of the flex cable. The flex cable must not have any kinks, sharp bends or twists which would concentrate the stress of the flexing and eventually would cause the electrical traces or conductor paths to break.
Flex cables have been used to accommodate movement of actuators and analogous devices in disk drives. In the past, proper orientation for the flex cable typically has been accomplished by attachment of the flex cable and its connections to a connector, which is further mounted to a circuit board. Examples of such implementations can be found in U.S. Pat. Nos. 5,291,355 and 5,214,550. In addition to the fact that the connections between the flex cable and the connectors can be sources of electrical faults in implementations, such as found in the above two cited patents, connectors with flex cable attachments consume precious space and ultimately may dictate the minimum height of the DASD.
An alternative approach which has been described in U.S. Pat. No. 5,278,709 adhesively attaches the flex cable to a stationary surface in the DASD housing to orient and mount the flex cable. Such adhesive attachment to the DASD housing creates problems because the adhesive may outgas over time and thereby contaminate the sealed environment of the DASD and possibly damage the disk surface, the slider, or other components enclosed within the DASD housing. Additionally, any such adhesive attachment of the flex cable to a rigid portion of the housing creates disassembly, rework, and repair problems if the device would need to be disassembled for repair or for other service.
While generally quite reliable in their intended use, flex cables with very thin dimensions are quite fragile due to the lack of physical strength of the flex cable and the conductive traces. If adhesively attached to rigid surfaces of the DASD housing, the flex cable may not be satisfactorily removed for repair or service to the DASD without damage to the cable and thereby would necessitate its replacement.